(Reuters) – U.S. health officials on Friday urged Americans to continue adhering to social distancing and other COVID-19 safety measures, and warned that states may need to reimpose strict restrictions if COVID-19 cases spike.

In recent weeks, experts have raised concerns that the reopening of the U.S. economy could lead to a fresh wave of infections. About half a dozen states, including Texas and Arizona, are grappling with a rising number of coronavirus patients filling hospital beds.

Officials from the U.S. Centers for Disease Control and Prevention (CDC) said the public should continue to maintain 6 feet of social distance, wash hands regularly and wear facial coverings to reduce the risk of infection.

“If cases begin to go up again, particularly if they go up dramatically, it is important to recognize that more mitigation efforts such as what were implemented back in March may be needed again,” said Jay Butler, the deputy director of infectious diseases at the CDC, who spoke to reporters along with CDC Director Robert Redfield.

As the United States reopens its economy, a number of U.S. states, including Texas, Arizona and Florida, have relaxed social distancing guidelines in recent weeks. Many U.S. states also do not require residents to wear protective masks.

Most Americans support stay-at-home orders and said they always or often wear face coverings in public , according to an online survey conducted early May of over 2,000 adults in New York City and Los Angeles. Most also said they would feel unsafe if restrictions were lifted.

The officials said summer public gatherings could boost infection rates, and urged participants to follow social distancing guidelines. They did not comment directly on rallies associated with the 2020 U.S. presidential election, but said the guidelines speak for themselves.